Elevator systems are useful for carrying passengers between various levels in a building, for example. There are various known types of elevator systems. Different design considerations dictate the type of components that are included in an elevator system. For example, elevator systems in high-rise and mid-rise buildings have different requirements than those for buildings that include only a few floors.
One issue that is present in many high-rise and mid-rise buildings is a tendency to experience rope sway under various conditions. Rope sway may occur, for example, during earthquakes or very high wind conditions because the building will move responsive to the earthquake or high winds. As the building moves, long ropes associated with the elevator car and counterweight will tend to sway from side to side. On some occasions rope sway has been produced when there are high vertical air flow rates in the elevator hoistway. Such air flow is associated with the well known “building stack or chimney effect.”
Excessive rope sway conditions are undesirable for two main reasons; they can cause damage to the ropes or other equipment in the hoistway and their motion can produce objectionable noise and vibration levels in the elevator cab.
A variety of sway mitigation techniques have been proposed. Most include some type of damper that is positioned to interrupt the side-to-side movement of the ropes at one or more locations in the hoistway. Other proposals include controlling movement of an elevator car during rope sway conditions. For example, U.S. Pat. No. 4,460,065 discloses detecting swaying movement of a compensating rope and limiting movement of the elevator car as a result.